This invention relates to an electrochemical zinc-oxygen cell comprising an oxygenelectrode containing a porous electrically conductive layer, a zinc electrode, a liquid basic electrolyte and a diffusion of zincate restricting membrane between the porous layer of the oxygen electrode and the zincelectrode. Such a cell is known from the French patent specification No. 1,492,284 and the thereby belonging patent of addition 91.138.
In electrochemical cells of this type the oxidant need not be contained in the cell but atmospheric air can be used as such. One side (the gas contacted side) of the oxygen electrode is in contact with the gas containing molecular oxygen, e.g. air, the other side (the liquid contacted side) with a suitable electrolyte. The electrode reactions take place in the pores, near the gas-liquid interface. The porous electrically conductive layer usually possesses electrocatalytic properties. The current generated, or accepted, across the electrode, is accumulated, respectively distributed by a collector.
In the known zinc-oxygen cells there is the problem of impairment of the electrocatalytically active material in the cathode by zincate ions, resulting in a decrease of the electrocatalytic activity. This impairment may even result in the pores of the cathode getting blocked by corrosion products. It would be possible to limit the consequences of this problem to some extent by raising the catalyst concentration in the cathode material and/or using a thicker electrocatalytically active layer. However, this calls for more, expensive electrocatalytically active material. Another possibility would be raising the gas pressure on the gas contacted side of the cathode. However, this can result in bubble formation on the electrode, with loss of the favourable properties.
It has already been suggested to introduce a membrane, for example an ion-exchanging membrane, which is permeable for electrolyte, between the zinc electrode and the oxygen electrode. This is not sufficient as the diffusion of zincate-ions to the oxygen electrode is not sufficiently prevented. In the cells of known type the internal electrical resistance is unacceptably high.
The object of the invention is to provide an electrochemical zinc-oxide cell in which the drawbacks outlined above are obviated.